Glass ionomer cement compositions and restorative methods

ABSTRACT

A restoration for restoring a lesion in a tooth and method for making the same. The restoration comprises a layer of glass ionomer cement bonded to the lesion and a layer of amalgam disposed on the layer of glass ionomer cement. The restoration is formed by the process of applying a layer of wet glass ionomer cement on the lesion, placing a wet dental amalgam directly on the wet glass ionomer cement, and allowing the wet glass ionomer cement and the wet amalgam to harden to bond the amalgam to the tooth. Various modifications to the glass ionomer cement are disclosed to either improve the bond of the restoration&#39;s amalgam to the tooth or to enhance the cement&#39;s use in various dental procedures. Also disclosed are various dental procedures using the restoration and method of making the restoration which results in the resolution of certain shortcomings of current like procedures.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of application Ser. No. 08/079,332,filed Jun. 18, 1993 now U.S. Pat. No. 5,382,286, which is acontinuation-in-part of application Ser. Nos. 07/942,375, filed Sep. 9,1992, now U.S. Pat. No. 5,252,122; 07/872,501, filed Apr. 23, 1992, nowU.S. Pat. No. 5,525,121; and 07/991,112, filed Dec. 16, 1992, now U.S.Pat. No. 5,273,574.

FIELD OF THE INVENTION

This invention relates to dental restorations, and, in particular, todental restorations using glass ionomer cement and amalgam.

BACKGROUND OF THE INVENTION

Since its introduction to the United States in the late 1970's, glassionomer cements have gained a great deal of popularity for use invarious dental procedures. The interest in using glass ionomer cementsfor a myriad of purposes stems from the cement's ability to bond to bothdentin and enamel, the fact that the cement is tooth-colored whenhardened, and because glass ionomer cements generally contain fluorideswhich are thought to minimize the occurrence of decay to the toothsurface to which the glass ionomer cement is applied. Initially, glassionomer cements were generally used for restorations. These glassionomer cements, known as Type II glass ionomer cements, are of a largerparticulate matter than are the Type I glass ionomer cements used forother purposes. When these Type II glass ionomer cements are used as arestoration material, the lesion in a tooth is prepared by standardtechniques as may be performed for cavity preparation for the placementof an amalgam restoration thereon; however, it may not be necessary tocreate an undercut for a glass ionomer restoration. Care must be takento make certain that the preparation is free of moisture as glassionomer cement in such an application is extremely susceptible to watercontamination and dehydration during the initial setting stage.

Type I glass ionomer cements are typically used as a base, liner, orluting agent. When used for these purposes, the surface of the toothagain must be substantially free from moisture during application aswell as throughout the hardening process of the glass ionomer cement. Inaddition to its use as restorations, base, liner or luting agent, glassionomer cements are also used for affixing restorations to a tooth. Forcomposite restorations, such as ceramic or porcelain prostheses, theglass ionomer cement is allowed to harden and then is etched beforeplacement of the composite restoration thereon. For those restorationscontaining metal, the glass ionomer cement need not be hardened first aswet glass ionomer cement is known to adhere to cast metals.

Glass ionomer cements are generally comprised of a powder componentcontaining aluminosilicate and a liquid portion. Often the liquidportion is expressed as containing polyacrylic acid, polymaleic acid,polyitaconic acid, or a copolymer of at least two of the acids. Theliquid portion may also comprise carboxylate polymers or carboxylic acidpolymeric structures, such as those including acrylic acid, maleic acid,crotonic acid, isocrotonic acid, methacrylic acid, sorbic acid, cinnamicacid, fumaric acids and the like. "New Aspects of the Setting ofGlass-ionomer Cements," Wasson et al., Journal of Dental Research; Vol.72, No. 2, February, 1993; pages 481-483. In all glass ionomer cements,the primary, reactions which cause the glass ionomer cement to harden iscross-linking, i.e., the cross-linking of polycarboxylate chains bymetal ions from the glass. Also, during setting, the acids of the glassionomer cement dissolve the glass structure to release metalconstituents of the glass. Metal carboxylates are formed during thesetting process. This may be distinguished from the primary settingreactions of acrylic cements which are other forms of polymerizationreactions. Though other forms of polymerization reactions may occur inglass ionomer cements, these reactions are secondary to thecross-linking reactions of the glass ionomer cement.

Recently, it was discovered that wet glass ionomer cement bonds wellwith wet amalgam. As disclosed in U.S. patent application Ser. No.07/942,375, filed Sep. 9, 1992, now U.S. Pat. No. 5,252,122 a dentalrestoration is formed by applying a layer of wet glass ionomer cement toa lesion in a tooth, placing a layer of wet amalgam directly on thelayer of wet glass ionomer cement, and allowing the cement and theamalgam to harden to thereby bond the amalgam to the tooth. Such arestoration is beneficial in that the cavity preparation need not beundercut for the placement of an amalgam restoration. Further, the glassionomer cement does not appear to be as moisture sensitive in such aprocedure. Finally, the creation of the restoration is less timeconsuming than is a restoration in which the glass ionomer cement ishardened and then etched before the lesion is filled with amalgam.

Because glass ionomer cements have so many appealing qualities to thedental profession, numerous variations of glass ionomer cements havebeen developed to enhance particular properties of the glass ionomercements for specific applications. For example, U.S. Pat. No. 4,738,722,discloses a glass ionomer cement containing additives such as zinc oxideand titanium oxide. These additives improve the glass ionomer cement byeliminating pulpal sensitivity and also affect the setting time of thecement. Specifically, reducing the setting time of the cement with theintroduction of these additives is beneficial when the glass ionomercement is used as a base, liner, or luting agent wherein it is desirableto have a quick setting cement for the completion of further proceduresthereafter.

In U.S. Pat. No. 4,064,629, large metal particles are added to a glassionomer cement. In this manner when the cement is used as a base orliner for an amalgam restoration, application of a wet amalgam to ahardened glass ionomer cement essentially results in thecross-amalgamation of the mercury in the amalgam with the large metalparticles in the cement. This additive assists in strengthening the bondbetween the hardened glass ionomer cement base and the amalgamrestoration.

Another approach to strengthening the glass ionomer cement withouteffecting its adhesive properties is disclosed in U.S. Pat. No.4,738,722. Specifically, manufacturers have been known to add the powdercomponent of an amalgam to the glass ionomer cement. Such an additivemay be particularly helpful when using a glass ionomer cement as arestoration. Yet another additive is disclosed in Japanese Patent No.2,275,731. In this patent, zinc oxide and zirconium oxide are added tothe glass ionomer cement to improve its resistance to disintegration andcrushing and to improve its hardening time.

Another problem associated with glass ionomer cement is its tendency toshrink as it dries in relation to a reduction in the environmentalhumidity. In response to this problem, an additive mixture to glassionomer cement comprising quartz sand, cristobalite flour and zirconiumsilicate was added in a study discussed in the article "Physical andMechanical Properties of Glass-Ionomer Cements", Elliott, et al.,British Polymer Journal, 1975, 9, 297-306. Though the additive mixtureassists in reducing shrinkage in a less humid environment, it was alsofound to reduce the compressive strength of the cement.

Disclosed in U.S. patent application Ser. No. 07/991,112, filed Dec. 16,1992, now U.S. Pat. No. 5,273,574 is an additive comprising zircon foruse with the wet glass ionomer cement to wet amalgam restorative methodof U.S. patent application Ser. No. 07/942,375, now U.S. Pat. No.5,252,122. The zircon additive, in this application of glass ionomercement, is thought not to interfere with any of the normal chemicalreactions of the glass ionomer cement while allowing the practitioner toadjust the color, handling characteristics, and the setting time of thecement.

In addition to modifying the glass ionomer cement, improvements havebeen made with regard to the wet glass ionomer cement to wet amalgambond by mixing an additive to the amalgam. Specifically, in U.S. patentapplication Ser. No. 07/872,501, filed Apr. 23, 1992, now U.S. Pat. No.5,252,121, additives from the group of metal salts, metal bases andmetal oxides are added to the amalgam to improve such a bond. Such anadditive may comprise, for example, the powder component of apolycarboxylate cement.

With each of the various dental procedures for which glass ionomercements are known to be used, it is desired to improve upon certaincharacteristics of this cement depending on the particular use of thecement. As previously noted, a relatively quick setting time is desiredwhen the glass ionomer cement is being used as a base, liner or lutingagent or when used to affix a composite restoration to a tooth. Thisdesire is based on the requirement for the glass ionomer cement to firstharden prior to the completion of subsequent dental procedures. Further,any improvements which can be made for any use of a glass ionomer cementwhich inhibits secondary caries or which strengthens the glass ionomercement are generally desirable.

In addition to serving as a restoration, amalgam has been used for avariety of dental procedures. For example, there are instances in whichit is desirable to build an amalgam post or an amalgam core forattachment of a prosthesis to the tooth. A post is defined as a solidstructure which extends into a hole in the tooth, generally a holeformed in the root canal of the tooth. A core extends above the roottooth surface and is generally of larger mass than is a post. Shouldamalgam be used to build a post or a core, generally, the tooth surfacemust be undercut to mechanically retain the amalgam within the undercuttooth structure after the amalgam has hardened. Such undercutting is notfeasible in all instances depending on the tooth structure remaining andfrom which the post or core is to extend. Thus, the use of amalgam postsand/or cores may not always be feasible even though desirable for theirknown strength and adaptability or formability within the tooth.Therefore, it is desired to develop a method for building an amalgampost and/or an amalgam core which does not require undercutting of theremaining tooth structure.

When an amalgam core is used for the application of a prosthesisthereon, difficulty for the dentist and the patient arises in the amountof time usually required for the completion of such a procedure. First,in many instances this involves a multi-step process whereby the core iscemented to the tooth, or, alternately, may involve the application ofan amalgam core as previously discussed. In either instance, the core orcement must be allowed to harden. Then, before the prosthesis may beapplied to the core with a cement, the core must be properly shaped forthe prosthesis or the prosthesis must be made to fit the shape of thecore. Again, a period of time expires in treatment. Now, the cement canbe used to affix the prosthesis to the core to harden. It is thereforedesirable to develop a method for applying both a core and a prosthesisthereon which consumes less time than is currently required.

Another dental procedure to which improvements may be made is that ofpost cementation. Generally, a hole is prepared in the canal of thetooth for receipt of a post. The cement is spinned or applied into thehole and the post is coated with a cement. The post is then placed intothe hole and the cement is allowed to harden such that the cement holdsthe post's place within the hole. For stainless steel and titaniumposts, a variety of cements may be used for this purpose; however, forthese posts, cements are known to be deficient to adequately provide thedesired rigidity and strength. Therefore, it is desired to provide amethod of post cementation that may be utilized with a post of anymaterial to increase the stability with which the post is retainedwithin the hole.

The application of sealants to teeth often poses problems desired to beovercome. In many instances, sealants are applied to a child's teethwith the intent of protecting the tooth. Regardless of the age of thepatient, the sealant, usually an acrylic, is applied after etching,rinsing and drying the tooth. The sealant is then allowed to harden.This procedure may take upwards of three minutes to complete. Duringthis period, it is very difficult to isolate moisture from the area tobe sealed. Such moisture may reduce the bond between the sealant and thetooth. Therefore, it is desired to develop a procedure for sealing teethwhich is less time consuming than the described procedure. In addition,it is desired to provide a sealant which may be used without etching thetooth surface to be sealed. Also, the life expectancy of acrylicsealants is typically five years. There are instances when this periodof time is not sufficient and it is therefore desired to develop asealant having a longer life span. Finally, acrylic sealants do notchemically inhibit the development of secondary caries. Therefore, it isdesired to inhibit such decay with the use of a sealant containingfluorides or like decay-inhibiting materials.

There are some instances in which it is desired to splint two teethtogether. Such a procedure may be necessary, for example, should a toothbe jarred loose as may be caused by an accident. Generally, theprocedure for splinting teeth together today involves cementing theadjacent teeth together by applying crowns thereon. Such a procedure istherefore costly. It is desired, then, to reduce the cost of splintingteeth together as may be necessary to resolve a temporary problem orwhen the patient is unable to afford a more expensive procedure.

In summary, glass ionomer cements have been used for a variety ofpurposes since their introduction. Variations on the chemicalcomposition of the glass ionomer cements have proved helpful in the useof glass ionomer cements for particular dental procedures and yetfurther improvements are desired. In addition, there are numerous dentalprocedures for which cementing techniques may be utilized and which ascurrently performed may exhibit difficulties, inconveniences or problemswhich are desirable to be addressed in the development of new orimproved methods.

OBJECTS OF THE INVENTION

Accordingly, it is one object of the present invention to provide anadditive for glass ionomer cement which improves the strength of thecement without altering its chemical reactions.

It is another object of the present invention to provide a method forbuilding an amalgam core or an amalgam post which does not require thatthe remaining tooth structure be undercut.

It is still another object of the present invention to provide a methodfor building a core and attaching a prosthesis thereto that is less timeconsuming to perform than is required with current procedures.

It is another object of the present invention to provide a postcementation method that may be used to cement any post (including thosemade of stainless steel or titanium) and which results in an increase inthe retentive forces.

It is still another object of the present invention to provide a dentalsealant which is less time consuming to apply than are acrylic sealants,is capable of being used to seal adjoining grooves in the tooth surfaceto be sealed without etching the tooth, has an increased life expectancyover acrylic sealants and inhibits the development of decay.

It is yet another object of the present invention to provide a methodfor splinting adjacent teeth together which is less expensive than theapplication of a crown over the teeth.

SUMMARY OF THE INVENTION

A restoration for restoring a lesion in a tooth comprises a layer ofglass ionomer cement bonded to the lesion and a layer of amalgamdisposed on the layer of glass ionomer cement. The restoration is formedby the process of applying a layer of wet glass ionomer cement on thelesion, placing a wet amalgam directly the layer of wet glass ionomercement, and allowing the cement and the amalgam to harden to therebybond the amalgam to the tooth. This process is also referred to hereinas the wet-to-wet process or method.

In one embodiment, the glass ionomer cement of the restoration includesdiamond microcrystals which increase the compressive strength of thecement and which provides a mechanism whereby the contraction of thecement during hardening can be controlled. By controlling thecontraction of the cement, the expansion of the amalgam occurring duringits hardening may be accommodated.

In another embodiment, the glass ionomer cement comprises an antibioticcompound to assist in reducing the possibility of secondary caries fromthe restoration. In yet another embodiment, the glass ionomer cementcontains at least one additive from the group of metals, metal salts andmetal oxides to improve the bond strength of the restoration. Wet dentalamalgam is mixed throughout the cement in another embodiment of theglass ionomer cement to further enhance the bond strength and to improveupon the cement's compressive strength.

Various methods are presented herein in which the restoration created bythe wet-to-wet process is used to resolve shortcomings of present dentalprocedures. An amalgam post or amalgam core is formed by the wet-to-wetprocess, thereby eliminating the need to undercut the tooth surface forretention of the amalgam. For cementing posts within a canal hole in atooth, the wet-to-wet process is utilized to assist in retaining thepost within the canal hole. This post-cementation method may be used forposts made of materials such as titanium which are presently difficultto cement to a tooth. Also, the wet-to-wet method is used in affixing aprosthesis to an amalgam core extending from the tooth which reduces theamount of time necessary to complete such a procedure. The wet-to-wetmethod is also used to quickly and easily seal a tooth or teeth as wellas adjoining grooves in the tooth with such a sealant having an improvedlife expectancy and resistance to decay when compared to acrylicsealants. In addition, the wet-to-wet method is used to splint adjacentteeth together at a cost that is significantly less than the applicationof a crown to the adjacent teeth.

DETAILED DESCRIPTION

U.S. patent application Ser. No. 07/942,375, filed Sep. 9, 1992, nowU.S. Pat. No. 5,252,122 incorporated herein by reference, discloses amethod for restoring a lesion in a tooth as well as a restoration formedby that method. Specifically, the method involves the steps of applyingwet glass ionomer cement to a lesion, placing wet dental amalgamdirectly on the wet glass ionomer cement, and allowing the wet glassionomer cement and the wet dental amalgam to harden. In this manner, theamalgam is bonded to the tooth. The restoration formed by this methodcomprises a layer of glass ionomer cement bonded to the tooth and alayer of amalgam disposed on the layer of glass ionomer cement. Themethod and restoration are advantageous in that no retentive pins oracid etching is required for bonding an amalgam restoration to thetooth. Also, a large lesion or cavity may be filled by such restorationwithout requiring that the tooth be undercut for the retention of such arestoration. Though disclosed as applicable to a lesion, the method mayutilized on any tooth surface. For example, a portion of the tooth maybe broken off and the method used to restore the tooth to its desiredform. The method may also be used to form an amalgam veneer on any toothsurface and may even be applied to a substantially vertical surface.

As previously mentioned herein, glass ionomer cements contain metalcarboxylates formed during the setting process of the cement. Theprimary reaction causing the glass ionomer cement to harden is thecross-linking of polycarboxylate chains by metal ions from the glass.Thus, a glass ionomer cement when wet is a carboxylate-containingcement. As used herein, and in the claims, the term glass ionomer cementencompasses cements or adhesives using this primary reaction ofcross-linking. Further, because the presence of metal carboxylates iscritical to the formation of the ionic bond of the amalgam to the toothin the method of U.S. patent application Ser. No. 07/942,375, now U.S.Pat. No. 5,252,122 (the "wet-to-wet" method), the cement mustnecessarily be carboxylate-containing. It is possible for acarboxylate-containing cement or adhesive to be comprised of cementsother than a pure glass ionomer cement to achieve the desired bond. Inaddition to cements comprising a glass ionomer cement and an additive oradditives thereto, the cement may comprise a mixture of different typesof cements and still be contemplated as within the scope of theinvention. For example, a mixture of glass ionomer cement and an acryliccement contains carboxylates and therefore may be utilized in thewet-to-wet method.

It will be appreciated by those of skill in the art that the wet-to-wetmethod does not require that the tooth to be restored first be etchednor does a primer need to be applied. This results in an expedientprocedure for restoring a tooth. However, it is possible that an etchantor primer is first applied to the tooth prior to the application of theglass ionomer cement. Though the application of an etchant and/or primerincreases the time necessary to create the restoration, it may bedesirable should its presence increase the bond of the amalgam to thetooth or should the dentist's preferences dictate the use of an etchantor primer.

Considering first the use of a primer, primers, sometimes referred to asdentin pretreatment materials, are used with acrylic bonding systems aswell as in other dental restorative procedures. In acrylic bondingsystems, the tooth is first etched and then a primer is applied to thetooth and allowed to harden. An acrylic bonding agent is then disposedon the primer and then the amalgam is applied to the bonding agent.Examples of primers used with bonding agents include hydroxyethylmethacrylate (HEMA), HEMA and glutaraldehyde, ferric acid, andphosphonated dimethacrylate combined with ethanol, water andcomphoroquinone. Though some primers may reduce the bond strength of theionic bond of the amalgam to the tooth in the wet-to-wet method, other,such as ferric chloride, may present ions which enhance the ionic bondof the amalgam to the tooth.

Though glass ionomer cements bond well to dentin, a dentist may desireto prepare the tooth surface with an etchant with the intent ofenhancing the bond of the restoration to the tooth. Examples of etchantsused today in dentin bonding systems as well as in other restorativeprocedures include ether-acetone, hydrogen peroxide and alcohol, citricacid, phosphoric acid and ethylenediaminetetraacetic. Application of anetchant to the tooth prior to the application of the glass ionomercement is contemplated to be within the scope of the invention as theglass ionomer cement is still applied directly to the tooth and an ionicbond between the amalgam and the tooth results from the application ofwet amalgam on the wet glass ionomer cement.

In terms of improvements to the glass ionomer cement as may be used inthe restoration and method (the "wet-to-wet" method) of U.S. patentapplication Ser. No. 07/942,375, now U.S. Pat. No. 5,252,122, it isdesirable for the glass ionomer cement to accommodate the knownexpansion of amalgam during the amalgam's hardening process. Theexpansion of amalgam is generally advantageous in that it assists insealing the amalgam restoration to the tooth. It is therefore preferablethat the glass ionomer cement not hinder the early setting expansion ofthe amalgam for this reason. By creating a glass ionomer cement whichcontrols the contraction while hardening at an amount substantiallyequivalent to the dimensional changes of wet amalgam in earlyamalgamation, the restorative bonding stress between the layer ofhardened glass ionomer cement and the layer of hardened amalgam areminimized. In this manner, few gaps between the layers result to therebyimprove the bond of the glass ionomer cement to the amalgam as well asthe bond of the amalgam to the tooth.

Glass ionomer cements containing inert additives, i.e., those additiveswhich do not appear to interact with the chemical reactions of the glassionomer cement, have been found to assist in minimizing the restorativebonding stress between the layer of hardened glass ionomer cement andthe layer of hardened amalgam. Zircon (zirconia silicate) disclosed asan additive to glass ionomer cement for the "wet-to-wet" method in U.S.patent application Ser. No. 07/991,112, filed Dec. 16, 1992, now U.S.Pat. No. 5,273,574 constitutes such an inert additive. Another inertadditive is diamond. According to the present invention, diamondmicrocrystals are added to the glass ionomer cement for the purpose ofreducing the restorative bonding stress between the layer of glassionomer cement and the layer of amalgam, as well as for improving theoverall strength of the glass ionomer cement. This "strength" refers tothe cement's compressive strength and its resistance to crushing anddisintegration. A glass ionomer cement comprising diamond microcrystalsmay be formed by adding diamond microcrystals to either the powdercomponent or the liquid component of the glass ionomer cement prior tomixing the powder and liquid together to form a wet cement. To result ina glass ionomer cement having acceptable handling characteristics for avariety of restorative purposes, diamond microcrystals comprise fromabout 0.1% by weight to about 50% by weight of the total weight of thecement. If, for example, the cement is to be utilized as a restorativematerial for filling a cavity, a greater percentage of diamondmicrocrystals is desirable. On the other hand, for use as a base, liner,or luting agent, a lower percentage of diamond microcrystals may bepreferable. It is worthy to note that the thickness of the resultingcement decreases with the addition of diamond microcrystals. Theadditive's affect on viscosity must also be taken into considerationwhen determining the appropriate amount for use in a particular dentalprocedure.

It will be appreciated by those of skill in the art that the diamondmicrocrystals not only increase the strength of the glass ionomercement, but the diamond microcrystals do so without interacting with thechemical reactions of the glass ionomer cement during hardening. Thus,diamond microcrystals are desirable for a variety of uses of glassionomer cements including the "wet-to-wet" method of restoring a lesionin a tooth disclosed in U.S. patent application Ser. No. 07/942,375, nowU.S. Pat. No. 5,252,122. Also, the diamond microcrystals may be added toglass ionomer cements used for other procedures well known in the art.For example, glass ionomer cement containing diamond microcrystals maybe used as a base, as a liner, as a luting agent or as a restorativematerial.

Because glass ionomer cements are carboxylate-containingadhesives/cements, and because the primary reaction occurring during thesetting of the glass ionomer cement is the cross-linking ofpolycarboxylate chains by metal ions from the glass, improvements to theglass ionomer cement may also be made by adding to the cement anadditive or additives in the form of a metal base, metal salt and/ormetal oxide. The presence of these metal additives further facilitatethe cross-linking of polycarboxylates with the metal ions of glassionomer cement. Such an additive may comprise from about 2% to about 50%by weight of the total weight of the cement and may be added to eitherthe liquid or powder components of the glass ionomer cement. The metal,metal salt, and/or metal oxide additive(s) may be a combination thereofand assists in increasing the bond strength of wet glass ionomer cementto wet amalgam.

One concern in creating an amalgam restoration is the potential for thedevelopment of secondary caries. If decay develops between the tooth andthe amalgam restoration, replacement of the amalgam restoration mayeventually be required. When replacing an amalgam restoration due to thepresence of decay, the decay must necessarily be removed, usuallyresulting in further loss of enamel and/or dentin. In one embodiment ofthe present invention, an antibiotic compound is added to the glassionomer cement with the intent of reducing the development of suchsecondary caries as well as any residual primary caries. The antibioticcompound may be added to either the powder or liquid components of thecement prior to mixing or may be added to the mixed cement prior to theapplication of the cement. Antibiotic compounds include chlorhexidine,tetramycin, penicillin, keflex, ampicillin, cephalosporin, and otherantimicrobial or antibiotic agents. The antibiotic additive may be addedin an amount comprising from about 0.1% by weight to about 35% by weightof the total weight of the glass ionomer cement. When used inconjunction with the "wet-to-wet" restorative method of U.S. patentapplication Ser. No. 07/942,375 now U.S. Pat. No. 5,252,122, the glassionomer cement containing an antibiotic compound not only assists inbonding the amalgam to the tooth, but provides an antimicrobial additiveto resist the development of secondary caries between the amalgam andthe tooth.

In another embodiment of the present invention, just triturated dentalamalgam is mixed throughout the glass ionomer cement. "Just triturated"is intended to mean wet dental amalgam wherein the amalgam powder andmercury components of the amalgam have been mixed and the mixture hasnot yet amalgamated or hardened. By adding wet amalgam to the glassionomer cement in amounts from about 20% by weight to about 70% byweight of the total weight of the composition, a strong restorativematerial results. Essentially, the wet-to-wet restorative method isutilized within this restoration as the wet amalgam resides within thewet glass ionomer cement. Such a composition has been found not toaffect the amalgamation process and the amalgam continues to amalgamatewithin the glass ionomer cement, i.e. the amalgam within the glassionomer cement hardens in concert with the hardening of the glassionomer cement. For such a restorative material, the glass ionomercement may be of a composition which accommodates the expansion of theamalgam within the glass ionomer cement such that a restoration usingthis composition does not place undue stress on the lesion or cavity inwhich the restoration is applied.

It will be appreciated by those of skill in the art that restorativematerial comprising wet (just triturated) amalgam in wet glass ionomercement may be used for dental procedures ordinarily requiring the use ofglass ionomer cement alone. In addition to using the restorativematerial as a restoration, it may be used as a base, liner, corematerial, or luting agent. The restorative material may also be usedwith the wet-to-wet restorative method of the present invention.

As previously mentioned herein, there are numerous dental procedures towhich improvements may be made. As disclosed herein, the wet-to-wetrestorative method of the present invention may be used to improve uponvarious dental procedures. In one embodiment of the present invention,to create an amalgam post which is to extend from a canal hole in atooth, glass ionomer cement is used to bond the amalgam post to thetooth according to the wet-to-wet method. Specifically, by applying thewet glass ionomer cement to the hole, packing the wet amalgam into thehole and allowing the amalgam and cement to harden, an amalgam post isformed. The resulting amalgam post may be used in concert withconventional dental procedures requiring a post. It will be appreciatedby those of skill in the art that this amalgam post may extend directlyabove the tooth surface without requiring the tooth surface be undercutas is necessary when amalgam is applied without the use of thewet-to-wet restorative method.

Similar to building an amalgam post, an amalgam core for a tooth may beformed using the wet-to-wet method. By applying a layer of wet glassionomer cement to the tooth, and then applying a layer of wet amalgam tothe layer of wet glass ionomer cement such that the wet amalgam extendsabove the root portion of the tooth, an amalgam core is formed upon thehardening of the glass ionomer cement and the amalgam. As with thebuilding of amalgam posts, no undercutting is required for building anamalgam core according to the present invention. Of course, the amalgamcore according to the present invention may be used in conjunction witha support member, such as a pin or post which extends above the toothsurface. By applying the amalgam intended to form the core about asupport member, the support member is utilized to assist in holding theamalgam core in place. It will be further appreciated that use of asupport member may be desired when restoring a large lesion or cavityusing the wet-to-wet method.

In another embodiment of the present invention, amalgam is used toassist the cementation of a post into a tooth. Specifically, for a toothhaving a canal hole therein, a post having a length greater than thedepth of the hole is placed into the hole after wet cement is applied toeither the hole or the post or both. For example, the cement may bespinned or applied into the hole and/or applied to the portion of thepost to be inserted into the canal hole. Use of the cement holds thepost in place in the hole. A portion of the post extends above the toothwhen placed in the hole. By placing cement about the post at the pointat which the post extends above the hole and bonding a wet amalgam tothe cement placed above the hole, and allowing the amalgam to harden,the amalgam and cement above the hole assist in retaining the postwithin the hole. Various amalgam bonding agents may be employed as thecement above the hole in this post cementation method, or toothstructure above the hole may be undercut for retention of the amalgamabout the post and above the hole. The wet-to-wet method is alsocontemplated for use in this post cementation method as well.Specifically, a glass ionomer cement is used and the amalgam is appliedto the glass ionomer cement above the hole before the cement hardens.This results in the bonding of the wet amalgam to the wet glass ionomercement. It will be appreciated by those of skill in the art that cementmay extrude from the hole after placing the post into the canal hole. Ifsuch an extruded cement results, it is not necessary to apply additionalcement above the post as the extruded cement may be used for the bondingpurpose.

It will be appreciated that the amalgam applied above the canal hole mayalso be bonded to the post itself. The post cementation method may beparticularly helpful when using an inert metal post (e.g. titanium orgold) as cements generally do not adhere as well to inert metal posts,even though amalgam bonds well with such posts. Though the use of inertmetal posts is desirable due to the material's strength, it has beenhindered due to the inability to secure these posts within the hole. Byusing the post cementation method described herein wherein the amalgamcontacts the post above the hole, the post is securely cemented withinthe hole by being bonded to the amalgam which is in turn bonded to thetooth. It will be appreciated by those of skill in the art thatregardless of the composition of the post, the placement of this amalgamcap at the top of the hole about the post further assists in retainingthe post within the hole. This is true whether or not the amalgamactually contacts and is bonded to the post itself.

The wet-to-wet restorative method of the present invention may also beused to adhere an amalgam core to the tooth for the placement of aprosthesis thereto. By placing wet glass ionomer cement on a lesion inthe tooth, packing the wet amalgam into the lesion such that the wetamalgam contacts the wet glass ionomer cement, an amalgam core is formedas previously described herein. A prosthesis may be cemented to theamalgam core with wet glass ionomer cement to form an amalgam core. Sucha prosthesis may be, for example, a crown or a bridge. It is alsocontemplated to be within the scope of the invention to cement theprosthesis over an amalgam core before the amalgam hardens. Thissignificantly reduces the amount of time required for the procedure ofbuilding a core and placing a prosthesis thereon as is done in the priorart. Specifically, the amalgam core may be applied directly over theglass ionomer cement without waiting for the cement to harden. Also, theprosthesis may be applied to the amalgam core before the amalgamhardens. It will also be appreciated that a support member, such as apin or a post, may be used in conjunction with the method of affixing aprosthesis to a core as discussed herein. Such a support member willfurther assist in retaining the core and prosthesis in position.

To address problems associated with the use of acrylic sealants, thewet-to-wet restorative method of the present invention may be utilized.Specifically, by applying a layer of wet glass ionomer cement on thesurface of the tooth to be sealed, placing a layer of wet amalgamdirectly on the wet glass ionomer cement thereby enabling the glassionomer cement to bond the amalgam to the tooth, and allowing the glassionomer cement and the wet amalgam to harden, the amalgam is bonded tothe tooth to form a seal. This method results in several advantages overthe application of acrylic sealants. First, the sealing method of thepresent invention is less time consuming than the method using acrylicsealants. Also, the glass ionomer/amalgam sealant is capable of sealingadjoining grooves in the tooth surface to be sealed without etching thetooth. Because the sealing method of the present invention may last alifetime, it results in a seal having an increased life expectancy overacrylic sealants which typically only last for five (5) years. The glassionomer/amalgam sealant also inhibits the development of decay. Thisinhibition of decay results from the fact that glass ionomer cementsgenerally comprise fluoride ions which resist the development ofsecondary caries.

In yet another embodiment of the present invention, the wet-to-wetmethod may be used to splint two adjacent teeth together. The splintingmethod utilizes the wet-to-wet restorative method. First, wet glassionomer cement is applied to adjacent surfaces of the teeth. Then, alayer of wet amalgam is placed onto the wet glass ionomer cement, andthe cement and amalgam are allowed to harden. In this manner, theadjacent teeth are bonded to each other upon hardening of the cement andamalgam. A fastener, such as a stainless steel wire, may be used withthe splinting method of the present invention to assist in splinting theadjacent teeth together. By drilling a hole in each of the teeth andcementing the ends of the fastener to the drilled holes prior to theapplication of the wet glass ionomer cement, the glass ionomer cementand amalgam is then applied about the fastener. This results in thefastener joining the adjacent teeth together in addition to teeth beingbonded together by the application of the glass ionomer cement andamalgam according to the wet-to-wet method of the present invention.

It will be appreciated by those of skill in the art that the splintingmethod of the present invention is less costly than is the conventionalsolution of placing crowns over the adjacent teeth. Further, thesplinting procedure is easily performed in a short amount of time andtherefore offers a more viable solution for a temporary problem to beresolved by splinting adjacent teeth together.

What is claimed is:
 1. A glass ionomer cement, comprising:a powder component comprising aluminosilicate and a liquid component comprising an unsaturated carboxylate containing monomer or polymer or both; and diamond microcrystals.
 2. The cement of claim 1 wherein the diamond microcrystals comprises from about 0.1% by weight to about 50% by weight of the total weight of the cement.
 3. The cement of claim 1 wherein the diamond microcrystals are included with either the powder component or the liquid component.
 4. A restoration for restoring a tooth, comprising:a layer of glass ionomer cement bonded to the tooth, the glass ionomer cement comprising a powder component and a liquid component as defined in claim 1, and diamond microcrystals; and a layer of amalgam disposed on the layer of the glass ionomer cement, the restoration being formed by the process of applying a layer of wet glass ionomer cement to the tooth, placing a layer of wet amalgam onto the layer of the wet glass ionomer cement, and allowing the glass ionomer cement and the amalgam to harden.
 5. The restoration of claim 4 wherein the diamond microcrystals comprise from about 0.1% by weight to about 50% by weight of the total weight of the cement. 